NATO confirmed on Wednesday (29 October) sighting four groups of Russian warplanes, "conducting significant military manoeuvres" over European airspace in the past two days.

"These sizeable Russian flights represent an unusual level of air activity over European airspace," said NATO.

Among the planes tracked down, were strategic bombers, fighters and tanker aircraft.

The planes were sighted over the Baltic Sea, North Sea/Atlantic Ocean and the Black Sea between Tuesday and Wednesday, said NATO.

The Russian planes were detected by NATO allies that had sent out aircraft to identify them and were tracking them on the ground as well.

"Scrambles and intercepts are standard procedure when an unknown aircraft approaches NATO airspace," said NATO.

Over a 100 intercepts of Russian planes have been registered so far in 2014, which is three times the figure reported in 2013.

NATO has recently warned that the Russian intervention in Ukraine has constituted the most significant threat to the US-Europe security since the Cold War.

Many of NATO's eastern members, like Poland and the Baltic states, have been concerned over Moscow's active role in Ukraine, which has driven NATO's airspace surveillance teams into overdrive.